linux-kernel - Re: [PATCH 2/2] lockdep: choose to continue lock debugging despite taint

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Message-ID: <20090410121515.GP21506@elte.hu>
Date:	Fri, 10 Apr 2009 14:15:15 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Frederic Weisbecker <fweisbec@...il.com>, Greg KH <gregkh@...e.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	LTP <ltp-list@...ts.sourceforge.net>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 2/2] lockdep: choose to continue lock debugging despite
	taint


* Frederic Weisbecker <fweisbec@...il.com> wrote:

> Lockdep is disabled after any kernel taints. This might be 
> convenient to ignore bad locking issues which sources come from 
> outside the kernel tree. Nevertheless, it might be a frustrating 
> experience for the staging developers or anyone who might develop 
> a kernel that happens to be tainted.

Good point. Not having lockdep coverage for drivers/staging/ just 
prolongs their transition - not good.

But instead of this:

>  void add_taint(unsigned flag)
>  {
> +#ifndef CONFIG_LOCKDEP_IGNORE_TAINT
>  	/*
>  	 * Can't trust the integrity of the kernel anymore.
>  	 * We don't call directly debug_locks_off() because the issue
> @@ -220,6 +221,7 @@ void add_taint(unsigned flag)
>  	 */
>  	if (xchg(&debug_locks, 0))
>  		printk(KERN_WARNING "Disabling lockdep due to kernel taint\n");
> +#endif

I'd suggest to not do the debug_locks_off() call if TAINT_CRAP. I.e. 
something like:

	if (!(flag & TAINT_CRAP) && debug_locks_off())
		printk(...);

will do the trick.

	Ingo
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